StellaLuna

Hey guys! I feel like a new kid who got lost on her way to the bathroom, but I really need some assistance here. My baby is a 2005 Subaru Impreza AWD wagon, 2.5 L SOHC, automatic, no mods, about 44000 miles. The check engine light went on (some time ago, really, it's been well over a month now) and the cruise control light flashes and there's no cruise control. From what I understand, the cruise control won't work as long as the CEL is on. We got the code pulled and it's a P2097, post-cat converter O2 mixture too rich. I've checked the prices and the damn sensor is about $379. The shop refuses to put on anything I buy myself and won't use Bosch or Walker parts because he says they'll "crap out after 3 months"-- they're quoting me $550 for the sensor alone, because apparently it's made of gold or will give me spontaneous orgasms or make the car fly or some other reason that it should be that much more expensive.
So, questions:
1. "Crap out after 3 months"? Is that true? I'm of the opinion that if they're still in business, Bosch and Walker can't be making such shitty parts that they would crap out after 3 months. Is there any reason why I shouldn't buy the sensor myself and find a mechanic who isn't a total ass to put it on?
2. My car doesn't have a Haynes or Chilton manual, otherwise I'd be tempted to buy one and put the sensor on myself. Any other suggestions about where to get a tech manual for this car? Subaru has some listed on the website, but you have to purchase a PDF which means I can't even see if it's the info I need before I buy it.
3. If I find the technical manual and my Dad is kind enough to get me a sensor (he's awesome), would it be a huge scary thing to attach? And how would I get the CEL light to go away?

Thanks, guys! If I'm missing info, let me know.

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